import fetch from 'node-fetch';
import * as fs from 'fs';
import * as path from 'path';
import mkdirp from 'mkdirp';
import { getIntrospectionQuery } from 'graphql/utilities/getIntrospectionQuery';
import { buildClientSchema } from 'graphql/utilities/buildClientSchema';
import { printSchema } from 'graphql/utilities/printSchema';

interface Options {
  method?: 'GET' | 'POST' | 'PUT' | 'DELETE';
  headers?: { [key: string]: string };
  json?: boolean;
}

/**
 *
 * Fetch remote schema and turn it into string
 *
 * @param endpoint
 * @param options
 */
export async function getRemoteSchema(
  endpoint: string,
  options: Options,
): Promise<{ status: 'ok'; schema: string } | { status: 'err'; message: string }> {
  try {
    const introspectionQuery = getIntrospectionQuery();
    const { data, errors } = await fetch(endpoint, {
      method: options.method,
      headers: options.headers,
      body: JSON.stringify({ query: introspectionQuery }),
    }).then(res => res.json());

    if (errors) {
      return { status: 'err', message: JSON.stringify(errors, null, 2) };
    }

    if (options.json) {
      return {
        status: 'ok',
        schema: JSON.stringify(data, null, 2),
      };
    } else {
      const schema = buildClientSchema(data);
      return {
        status: 'ok',
        schema: printSchema(schema),
      };
    }
  } catch (err) {
    return { status: 'err', message: err.message };
  }
}

/**
 *
 * Prints schema to file.
 *
 * @param dist
 * @param schema
 */
export function printToFile(
  dist: string,
  schema: string,
): { status: 'ok'; path: string } | { status: 'err'; message: string } {
  try {
    const output = path.resolve(process.cwd(), dist);

    if (!fs.existsSync(output)) {
      mkdirp.sync(output);
    }
    fs.writeFileSync(output, schema);

    return { status: 'ok', path: output };
  } catch (err) {
    return { status: 'err', message: err.message };
  }
}

export async function main(endpoint): Promise<void> {
  /* Headers */
  const defaultHeaders = {
    'Content-Type': 'application/json',
  };

  /* Fetch schema */
  const schema = await getRemoteSchema(endpoint, {
    method: 'POST',
    headers: defaultHeaders,
    json: false,
  });

  if (schema.status === 'err') {
    console.error(schema.message);
  } else {
    console.log(schema.schema);
  }
}

main(process.argv[2]);